This invention relates to a gas turbine engine, more particularly modular gas turbine engines which include a compressor and gasifier module, a turbine case module and a power output module. This type of gas turbine engine may be disassembled into the three major components with the compressor and gasifier turbine wheel remaining with the compressor and gasifier section while the power output turbine wheel remains with the power output module. The case, constituting the third portion of the turbine, interconnects the compressor and gasifier turbine section with the power output section. Assembly of this gas turbine engine is the subject of U.S. patent application, Ser. No. 630,476, now U.S. Pat. No. 4,030,288 and the Continuation-in-Part filed therefrom both assigned to the assignee of this application.
The assembly of gas turbines has taken many forms, as discussed in the above-mentioned case. One particular problem encountered in assembly involves the installation of turbine shafts in the various modules. In particular, the gasifier turbine shaft must be installed in the compressor and gasifier turbine section and the power turbine shaft must be installed in the power turbine section prior to assembly of the engine. However, to fixedly rotatably associate the shafts with the associated sections, it has been necessary to work in extremely confined spaces for the installation of retaining nuts and bearings associated with the shaft. To work in such confined spaces not only is difficult, it also raises the concomitant problem of alignment of the shafts which is so critical in high speed gas turbine engines of the type described herein. To compound the problem, quite frequently a part or a tool is dropped in the turbine case. Due to the confined spaces, it has been found extremely difficult to retrieve such dropped parts or tools. In some cases it has become necessary to completely disassemble the engine to retrieve lost parts and tools.
Lubrication of the bearing associated with a turbine shaft in either the compressor and gasifier module or the power turbine module is particularly important. The problem of lubrication is compounded by the heat which is inherent in all gas turbine engines. It is to be understood that the heat in the gasifier section is, of course, considerably higher than that found in the power turbine section, although the problems are similar. It is well-known that efficient operation of the turbine is dependent upon extremely high temperatures in the gasifier turbine section itself. However, to increase the temperatures beyond a certain point may cause failure of the various component parts of the turbine with disastrous results. Various schemes to provide cooling fluid, such as compressed air to the turbine wheel, have been disclosed. However, in most cases the cooling method relates to axial flow compressors wherein the gasifier turbine shaft is of hollow construction and cooling air may be communicated therein directly from the compressor section. In turbine engines with radial flow compressors such as that disclosed herein, the compressor turbine shaft, or in the power section the power shaft, is generally solid. Therefore, it has proved difficult to communicate cooling fluid to or near the center of rotation of the shaft to be deflected radially outwardly of the shaft for cooling of the various rotating parts associated with the turbine wheel.
To provide both lubrication and cooling fluid at generally the same locale on the turbine shaft poses a particularly difficult problem.